A hybrid electric vehicle (HEV) can be propelled by an engine and a traction battery. A plug-in hybrid electric vehicle (PHEV) includes a traction battery that can be charged by electrically connecting it to an external power source. A battery electric vehicle (BEV) does not include an engine and is propelled only by a traction battery. HEV's, PHEV's and BEV's are three examples of vehicles that are at least partially propelled by a fraction battery. In such applications, the traction battery can include a battery pack having individual cells that are charged and discharged during operation.